True soaps are created through a saponification reaction in which fats, more appropriately, fatty acids, are neutralized with a base. To ensure that the reaction is driven to completion, it is common practice to employ an excess of base. Because soaps are generally compatible with antimicrobial agents, they are often used in liquid antimicrobial hand washes. Such soap-based antimicrobial hand washes are found in numerous markets including healthcare, food services, and consumer.
Antimicrobial agents are selected from a variety of classes, including bisguanidine (e.g., chlorhexidine digluconate), diphenyl compounds, benzyl alcohols, trihalocarbanilides, quaternary ammonium compounds, ethoxylated phenols, and phenolic compounds, such as halo-substituted phenolic compounds, like p-chloro-m-xylenol (known as “pcmx”) and 2,4,4′-trichloro-2′ hydroxy-diphenylether (known as “triclosan”). Although these antimicrobial agents are used in numerous hand wash formulations, they are not without some detrimental properties. Antimicrobial agents are typically irritating to the skin. And while skin irritancy is a concern for any cosmetic or drug formulation, it is even more pertinent to hand washes because of the sensitivity of the body areas treated. There is a need to minimize the amount of antimicrobial agent present in a hand wash formulation, in order to minimize the irritancy thereof. But by reducing the amount of antibacterial agent present, it is expected that the antimicrobial properties of the hand wash will also be reduced, and, thus, there exist competing desires to reduce antimicrobial agents while maintaining antimicrobial efficacy.
Another important concern for a wash formulation is the aesthetics of the product. For example, the public has come to associated foaming ability with cleaning ability, and, as a result, consumers are less likely to purchase a wash formulation that does not foam while washing. This consumer perception drives those in the market to formulate washing products which produce copious amounts of foam. As mentioned above, irritancy is a concern. The color and odor of a wash formulation is also important. When soaps are used in conjunction with antimicrobial agents, they do not present the best of each of these desired properties. Although the presence of the soap allows for a reduction in the amount of antimicrobial agent while maintaining a relatively high log kill, antimicrobial soap products tend to irritate the skin. Thusly, skin conditioning agents need added to produce an aesthetically pleasing hand wash.